Preheat oven to 400°F. Roll out pastry on floured surface to 12-inch square. Cut out four 5 1/2-inch rounds. Place on parchment-lined baking sheet; bake until golden, about 15 minutes. Cool on sheet. Can be made 1 day ahead. Wrap airtight and store at room temperature.

Preheat oven to 400°F. Whisk cream and flour in small bowl. Melt butter in large skillet over medium heat. Add leeks and sauté until tender, about 10 minutes. Add andouille and garlic and sauté 4 minutes. Add white wine or vermouth; simmer until liquid evaporates, about 3 minutes. Add seafood stock mixture and thyme. Bring to simmer. Add potato and green onion and cook uncovered until potato is tender, about 6 minutes.

Add cream mixture to skillet; stir. Simmer until sauce thickens and boils, about 3 minutes. Reduce heat. Add shrimp; simmer until just opaque in center, about 3 minutes. Season with salt and pepper.

Divide hot filling among four 1 1/4-cup baking dishes. Top each with pastry round. Bake until filling bubbles, about 5 minutes.